Lighting device for operative site without cast shadow

ABSTRACT

A lighting device for an operational field of the “cast shadow” type, which is particularly useful for but not limited to field of dental surgery, includes a lighting head which is fed with light by at least one cord of optical fibers for directing the light produced by a light generator placed at a distance from the lighting head. The light generator is provided with a mechanical system for moving an inlet end piece of the cord away from or closer to a lamp which serves as the light generator. The lighting head is further configured to project the approximately rectangular light spot which is required for illuminating the operational field onto the work zone.

The present invention concerns a lighting device for an operationalfield of the type without any cast shadow, particularly but notexclusively limited to the dental surgery field, including a lightinghead fed with light by cords of optical fibres directing the lightproduced by a light generator.

There already exist lighting devices for limiting cast shadows. Thedevices most currently used in the medical or dental field areshadowless lamps® comprising a lighting head having a glass parabolicreflector associated with one or several lamps or sets of mirrors.

One of the drawbacks of shadowless lamps® is that their light source islocated at the level of the lighting head and produces a quantity ofheat in a work zone prejudicial for practicians and patients.

Another drawback of this type of lighting is its significant volumerendering it relatively bulky.

Systems have already been put forward for lighting a targeted zone fedby optical fibre and an off-set light source for limiting the heat givenoff at the level of the operational field. For example, in this respectone could cite the lighting device described in the patent FR 1 431 405.However, this device retains a relatively significant volume.

Moreover, it is unable to fully satisfy the need of localised lighting,especially in the dental field, namely obtaining a luminous zone, notcircular but having an approximately rectangular shape.

The object of the present invention is to have a product able to obtainthese performances whilst also reducing the amount of heat in the workzone.

In accordance with the invention, this result is obtained with alighting device for an operational field of the cast shadow type,particularly by not exclusively limited for dental surgery, including alighting head fed with light by at least one of the cords of opticalfibres directing the light produced by a light generator placed at acertain distance from the lighting head, characterised in that the lightgenerator comprises a mechanical system for moving away or bringingcloser a start end piece of the cords with respect to a light generatorlamp.

In addition, the lighting head comprises means to project onto the workzone an approximately rectangular light spot required for illuminatingthe operational field.

According to one variant, the lighting head comprises:

at the frontal portion, at least two rear flat face aspheric lensesarranged on both sides of the longitudinal axis of the lighting head andhaving an angular positioning a with respect to the longitudinal axisallowing convergence of the light issued at the outlet by the twolenses,

an optical fibre cord end directed perpendicular to the rear flat faceof each aspheric lens, the optical fibres having at the fibre outlet atthe level of the end an oblong-shaped section.

The angular positioning α with respect to the longitudinal axis ispreferably about 5.5° and the distance between the frontal portion ofthe end and the flat rear face of each aspheric lens is about 35 mm.

Thus, the device of the invention is able to obtain a rectangular lightspot with dimensions of 10×20 to 70 cm of the lighting head.

According to a second variant, the lighting head comprises a concavereflector receiving the light from an outlet end piece of an opticalfibre cord and sending it towards the operational field.

The invention shall be more readily understood from a reading of thefollowing description with reference to the accompanying drawings onwhich

FIG. 1 is a skeleton diagram of a lighting system according to a firstvariant,

FIG. 2 is a cutaway bottom view of a lighting head according to a firstvariant,

FIG. 3 is a front view of the lighting head of FIG. 2,

FIG. 4 is a diagrammatic of the top of the light generator,

FIGS. 5a and 5 b are respectively cutaway side and front views of a cordend of optical fibres,

FIG. 6 is a cutaway top view of a lighting head according to a secondvariant,

FIG. 7 is a perspective view of the light outlet and the reflector ofthe variant of FIG. 6.

Reference is first made to FIG. 1.

The lighting device for an operational field of the type without anycast shadow is made up of a lighting head (1), cords of optical fibres(2) for directing to the lighting head (1) the light produced by a lighta generator (3) ) placed at a certain distance from the lighting head(1). By moving the light source away from the work zone, the use of theoptical fibres makes it possible to significantly reduce the amount ofheat and thus contribute in protecting the practician and patient.

FIGS. 2, 3, 5 a and 5 b represent a first variant of the lighting head(1).

The lighting head (1) consists of a housing (4) having possibly atrapezoidal shape, comprising at its frontal portion a lens support (5)made for example of a moulded, aluminium or composite material.

The lens support (5) comprises two housings (6) with shoulders (7) witha diameter of for example 45 mm in which two aspheric lens (8) with aflat rear face (11) are mounted having the same external diameter as thehousing and fixed into the latter by means of glueing or by any otherfixing element.

Advantageously, the aspheric lens made of glass for example could havean external diameter of 45 mm, a thickness of 15.7 mm and a focaldistance of 42 mm.

The centre distance (E) of the housings (6) may be 140 mm with anangular positioning of each housing of about 5.5° with respect to thelongitudinal axis (9) of the lighting head so as to allow the sameangular positioning of the axes (21) of the aspheric lenses (8).

The lighting head further comprises an optical fibre cord end (10)directed perpendicular to the rear flat face (11) of each aspheric lensalong the optical axis of the latter.

Each end (10) of the cord (2) is mounted in the lighting head (1) withthe aid of fasteners (12) for orientating the end (10) in rotation andfor positioning said elements angularly and in depth with respect to thelenses (8), said fasteners (12) further comprising pressure screws (notshown) for immobilising the ends after their positioning has beenadjusted.

As shown on FIGS. 5a and 5 b, the ends (10) of the optical fibre cordconsist of a cylinder body (27) made of aluminium for example fittedwith a central bore shaped so as to have partly at least one oblongsection (20) for similarly shaping all the fibre outlets so as toproduce a rectangular luminous spot with rounded angles at the level ofthe work zone.

The fastener elements made of machined aluminium are screwed onto asupport (not shown) in the lighting head.

Each lens is associated at the lens inlet or outlet (see FIG. 2) with afilter (13) made of glass or PMMA with at least one hammered aspectrelief face for correcting the aberration of the light rendered by saidfilters.

Each filter (13) is preferably placed as close as possible to the lensinlet (see FIG. 2) or outlet of the latter and shall be mechanicallyfixed to the lens support (5) by means of stapling, flanging or glueing.

Reference is now made to FIGS. 6 and 7 showing a second variant of thelighting head which comprises the same case (4) as in the first variant.

The optical fibre cord (2) arrives via the rear of the case and movesunder a reflector (29) applied against the bottom and inside of thecase.

The end of the optical fibre cord is bent back so that the end piece(30) comprising a “wide field” lens system (31) is directed towards thereflector (29).

Said reflector (29) has a specific peripheral shape, for exampleapproximately rectangular measuring 10×20 cm and its surface is concave.

Said reflector (29) can be made of glass or polished metal or of plasticcoated with any material reflecting the light so as to send the light tothe front of the lighting head (1).

In this variant, the oval or rectangular shape of the luminous spot isgiven by the shape of the concave reflector (29).

By means of the system for positioning the start end pieces of theoptical cords to be described subsequently, the light coming out of theoutlet end pieces (30) no longer comprises rays IR to be eliminated andit is possible to use a simple reflecting material for the reflector anda simple glass pane (32) at the front of the head (instead of expensivedichroic glass).

The paragraphs which follow apply to the two embodiment variants.

Advantageously, a cord (2) is made up of a grating of optical fibres,such as about 80 fibres protected by a sheath (14) made for example ofPVC, said sheath being nested and glued to one extremity in acylindrical start end piece and the other in the end (10).

The fibres are preferably plastic optical fibres preferably made of PMMAhaving for example a diameter of 0.5 mm.

The specific choice of PMMA optical fibres makes it possible to keep acolour temperature of about 5400° K corresponding to an extremely whitelight which is not the case for glass optical fibres which tend to lowerthe colour temperature, the light becoming more yellow.

The fibre cord or the two fibre cords (2) comprise at the fibre inlet agiven cylindrical start end piece (15) intended to be positioned at theoutlet of the light generator (3).

The cylindrical end piece (15) preferably comprises machined grooves(22), for example preferably extremely closely placed grooves, saidgrooves making it possible to dissipate the heat produced by the lightgenerator by using natural ventilation.

However, it is also possible to use other forms of ventilation for thecylindrical end piece.

The light generator (3) (see FIG. 4) preferably comprises amicro-discharge lamp (16) with an electronic ballast ellipsoid reflector(17) made for example of polished aluminium with a lamp with an outputof 35 or 50 W, a voltage of 85 volts able to vary by ±20%.

The light generator comprises further an electronic item of equipmentsuch as in its constitutive elements and which is not going to bedescribed here.

The light generator further comprises an outlet (18) fitted with amachining part (19) for nesting the common start end piece (15) of theoptical fibre cords (2) with a system for adjustment on two axes (23,24) for alignment on the lamp, said part comprising a concentric borewith immobilisation means (not shown) of said end piece, such as apressure screw placed transversally with respect to the machining part.

The positioning on two axes could also be effected directly at the levelof the lamp. In this embodiment, the common start end piece of the cordswould then remain fixed.

Advantageously, said machining part (19) comprises a mechanical system(not shown) making it possible to move away or move closer the commonstart end piece of the cords with respect to the lamp as indicated bythe double arrow (25) so as to adjust the intensity of the luminous flowproduced. Thus, it is possible to make the luminous flow vary from 5,000to 25,000 lux by acting on the start end piece.

Advantageously, a filter (26) for protecting the optical fibres isinserted between the common start end piece (15) and the lamp (16), saidfilter being mounted for example in a metal support with springflanging.

Said protection filter is thus able to protect the optical fibres fromfirstly ultraviolet rays which, over a period of time, can result inyellowing of the material of the optical fibres, and secondly frominfrared rays, an excessively high temperature on the start end piece ofthe fibres possibly significantly altering the structure of the opticalfibres, for example via the decomposition of resins used as a binder, orvia the combustion of the PMMA fibres.

The protection filters can be made of glass or quartz with dimensions of30×30 mm with a thickness of several millimetres.

Advantageously, a second filter (28) can be inserted between the commonstart end piece (15) and the lamp (16) so as to increase the colourtemperature (for example so as to strengthen the “blues”).

Advantageously, the lighting head and the generator are fixed with anarticulated arm in which the optical fibre cords are positioned.

The entire system (namely the lighting head, the light generator, thearticulated arm with the optical fibre cord) could be mounted on alltypes of support and in particular on all types of dental equipment inthe same way as for example with conventional shadowless lamps®.

What is claimed is:
 1. A lighting device for producing an operationalfield without any cast shadow, for use in fields including dentalsurgery, comprising a lighting head, a light generator having a lamp andplaced at a distance from the lighting head, and at least one opticalfiber cord for receiving and directing light produced by the lightgenerator, wherein the cord includes an inlet end piece, and wherein thelight generator includes a mechanical system coupling the lightgenerator and the inlet end piece, for moving the inlet end piece of thecord closer and away from the lamp of the light generator.
 2. Thelighting device of claim 1 wherein the lighting head includes an outletend piece associated with the optical fiber cord and configured toproject an approximately rectangular luminous spot onto a work zone, forilluminating the operational field.
 3. The lighting device of claim 2wherein the optical cord has optical fibers, wherein the end of theoptical cord defines a fiber outlet, and wherein the fiber outlet has anoblong-shaped section.
 4. The lighting device of claim 2 wherein thelighting head has a frontal portion and a longitudinal axis, wherein thefrontal portion includes at least two lenses placed on opposite sides ofthe longitudinal axis of the lighting head, and wherein the lenses havean angular positioning a with respect to the longitudinal axis, forcausing a convergence of light issuing from the lenses.
 5. The lightingdevice of claim 4 wherein the lenses are aspheric lenses.
 6. Thelighting device of claim 5 wherein each lens has a flat rear face, andwherein the optical cord has an end directed perpendicular to the flatrear face of the lens.
 7. The lighting device of claim 6 wherein the endof the optical cord is mounted in the lighting head so that the end isoriented in rotation, and so that the depth and angular positioning ofthe end is fixed with respect to the lenses.
 8. The lighting device ofclaim 7 wherein the optical cord is mounted in the lighting head byfasteners.
 9. The lighting device of claim 6 wherein the angularpositioning a is about 5.5° with respect to the longitudinal axis, andwherein the end of the optical cord is separated from the flat rear faceof each aspheric lens by a distance of about 35 mm.
 10. The lightingdevice of claim 4 wherein each lens further includes a filter forrectifying aberrations of light issuing from the lenses.
 11. Thelighting device of claim 10 wherein the filter is located at an inlet ofthe lens.
 12. The lighting device of claim 10 wherein the filter islocated at an outlet of the lens.
 13. The lighting device of claim 1wherein the lighting head includes a concave reflector for receiving thelight from an outlet end piece associated with the optical fiber cordand for directing the light to the operational field.
 14. The lightingdevice of claim 13 wherein the reflector is formed of a materialselected from the group of materials consisting of polished metal,reflecting glass and coated plastic.
 15. The lighting device of claim 13wherein the reflector is approximately rectangular.
 16. The lightingdevice of claim 13 wherein the outlet end piece includes a wide fieldlens system.
 17. The lighting device of claim 1 wherein the inlet endpiece is cylindrical and wherein the cylindrical end piece has machinedheat dissipation grooves.
 18. The lighting device of claim 1 wherein thelight generator includes a micro-discharge lamp with an electronicballast and an ellipsoid reflector.
 19. The lighting device of claim 1wherein the light generator further includes an outlet provided with amachining part for receiving the inlet end piece, and wherein themachining part is adjustable along two axes relative to the lamp. 20.The lighting device of claim 19 wherein the machining part furtherincludes a concentric bore with means for immobilizing the inlet endpiece.
 21. The lighting device of claim 10 wherein the machining partincludes the mechanical system for moving the inlet end piece associatedwith the cord closer and away from the lamp of the light generator. 22.The lighting device of claim 1 which further includes a first filter forprotecting the optical fibers inserted between the inlet end piece andthe lamp.
 23. The lighting device of claim 1 which further includes asecond filter for raising the color temperature inserted between theinlet end piece and the lamp.
 24. The lighting device of claim 1 whereinthe optical fibers are plastic fibers.